| 摘要 |
<p>A process of imparting a predetermined curvature to a sheet of thermoplastics material in which a thermoplastics sheet is bent by placing it against a face of a bending form. The form having a moulding surface area of the required curvature. The process includes heating the thermoplastics sheet and causing or allowing it to conform to the moulding surface area. The thermoplastics sheet is formed oversized and is bent by placing it against a bending form having a moulding surface area portion of the required dimensions and curvature which is surrounded by a bending form surround. Next, the thermoplastics sheet is heated and caused or allowed to conform to the moulding surface area portion while its oversized margins are supported by the bending form surround. Thereafter, the thermoplastics sheet is cooled at a rate slow enough to maintain such conformity, and then the thermoplastics sheet is trimmed to size.</p> |
